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THE 

MANURES 

3I0ST ADVANTAGEOUSLY APPLICABLE TO THE 

VARIOUS KINDS OF SOILS, 
AND THE CAUSES 

OF 

THEIR BENEFICIAL EFFECT 

IN EACH PARTICULAR INSTANCE. 



.,,... .Idoneus Patriae, sit Utilis Agris. 

yuv. Sat. 14. 






BY 

RICHARD KIRWAN, Esq. f. r. s. & m. r. i. a. 

Author of the Elements of Mineralogy, &c. 



FROM THE SIXTH LONDON EDITION. 



PHILADELPHIA : 

Printed by KIMBER, CONRAD, and CO. 

No. 93 market street, ^ 170 south second strre 

iaor. 






w 









V 






WHAT ARE THE MANURES MOST ADVANTAGE- 
OUSLY APPLICABLE TO THE VARIOUS SORTS 
OF SOILS ; 

AND, 

WHAT ARE THE CAUSES OF THEIR BENEFICIAL 
EFFECT IN EACH PARTICULAR INSTANCE. 



. . Idoneus Patriae, sit Utilis Agris. 

JUVEN. SAT. 14. 



AGRICULTURE is the art of mak- 
ing the ear r h produce the largest crop of 
useful vegetables at the smallest expense* 
It has often been remarked, that amidst 
the various improvements which most of 
the practical arts have derived from the 
progress lately made in natural philosophy 
and chemistry, none have fallen to the 
share of agriculture, but that it remains 
nearly in the same state in which it existed 
two thousand years ago. I am far from 
allowing the truth of this observation, taken 



in its totality ; to refute it, we need only 
compare the writings of Cato, Columella, 
or Pliny, with many modern tracts, or still 
better, with the modern practice of our 
best farmers. It must be granted, how- 
ever, that vague and fortuitous experience 
has contributed much more to the present 
flourishing state of this art than any gene- 
ral principles deduced from our late ac- 
quired knowledge, either of the process 
of vegetation, or of the nature of soiis ; 
but the skill thus fortuitously acquired is 
necessarily partial, and generally local ; 
the very terms employed by the persons 
who most eminently possess it, are gene- 
rally of a vaorie and uncertain sicrnifica- 
tion. Thus Mr. Young, to whose labours 
the world is more indebted for the diffu- 
sion of agricultural knowledge than to 
any writer who has as yet appeared, re- 
marks, That in some parts of England, 
here husbandry is successfully practised, 
any loose clay is called marl* ; in others, 
marl is called chalkf ; and, in others, clay 
is called loam f. Philosophic researches 
have been made, but not yet sufficiently 
noticed: much] nformation may be derived 
from Mo:. 1. ur Bu Hamel, and much 
more from the well-directed experiments of 

* Fir«?t Eastern Tour, 178. 
t 2 Bath Mem. 192, 220. \ 2 Bath Mem. 137. 



Mr. Tillet*. Immense strides have been 
made in this career, by the illustrious Berg- 
man ; Dr. Priestley's experiments have 
thrown a new light on this, as well as on 
every other object of natural philosophy. 
Mr. Lavoisier's new theory explains ma- 
ny circumstances, before inexplicable ; 
discoveries of great importance have been 
made by Mr. Senebier and Dr. Ingenhouz : 
even Mr. Young has not always confined 
his attention to the mere practical part, 
but sometimes happiiy extended it to ob- 
jects of a more general and speculative na- 
ture ; but the fullest light, perhaps, has 
been thrown on this subject by the late 
discoveries of Mr. Hassenfraz.f 

If the exact connexion of effects, with 
their causes, has not been so fully and so 
extensively traced in this as in other sub- 
jects, we must attribute it to the peculiar 
difficulties of the investigation. In other 
subjects, exposed to the joint operation of 
many causes, the effect of each, singly 
and exclusively taken, may be particularly 
examined ; the experimenter may work in 
his laboratory with the object always in his 
view; but the secret processes of vegeta- 
tion take place in the dark, exposed to the 
various and indeterminable influences oi 

■ Mem. Par. 1772. f Annates ChjTniques, Vol 13, H. 



6 

the atmosphere, and require, at least, half 
a year for their completion. Hence the 
difficulty of determining on what peculiar 
circumstance success or failure depends ; 
the diversified experience of many years 
can alone afford a rational foundation for 
solid specific conclusions. It cannot there- 
fore, be expected, that new, decisive, and 
direct experiments should be laid before 
the Academy within the time prescribed 
for answering this question. The resolu- 
tion of the first part must be deduced from 
a statement of facts long established by 
multiplied experience ; and that of the se- 
cond, by the application of more general 
principles to the explanation of those 
facts.— But before we proceed to either 
branch of this question, the distinctions 
and denominations, both of soils and ma- 
nures, must be exactly settled and accu- 
rately defined. 



CHAP. I. 

OF SOILS AND MANURES. 



SECTION I. 

OF SOILS. 



LAND, considered as the basis of ve- 
getation, is called soil. 

Soils consist of different combinations of 
two or more of the four primitive earths, 
namely, the calcareous (which I some- 
times call mild calx) magnesia, argill, and 
the silicious. For a more accurate de- 
scription of these I must refer to books of 
mineralogy ; and shall only remark, that 
by calcareous earths are meant chalk, and 
all stones that burn to lime. They are 
easily distinguished by their property of 
effervescing with acids. 

Magnesia is never found alone ; its 
distinguishing character consists in afford- 
ing a bitter salt, generally called Epsom 
Salt, when combined with the vitriolic 
acid. 

Argill is that part of clay to which this 
owes its property of feeling soft and one- 



8 

tuous, and of hardening in fire ; it is 
difficultly soluble in acids, and scarce ever 
effervesces with them. When combined 
with the vitrolic acid, it forms alum. 

Silicioas Earth is often found in a stony 
form, such as flint or quartz ; and still 
more frequently in that of a very fine sand, 
such as that whereof glass is made. It 
does not effervesce, nor is it soluble in any 
of the common acids. 

To these we may add Iron, in that im- 
perfect state in which it exists when reduc- 
ed to rust, and commonly called Calx of 
Iron. 

The soils most frequently met with, and 
which deserve a distinct consideration, are 
clay, chalk, sand, and gravel, clayey loam, 
chalky loam, sandy loam, gravelly loam, 
ferruginous loam, boggy soil, and heathy 
soil, or mountain, as it is often called. 

Clay is of various colours ; for we meet 
with white, grey, brownish red, brownish 
black, yellow or bluish clays ; it feels 
smooth, and somewhat unctuous : if moist, 
it adheres to the fingers, and if sufficiently 
so, it becomes tough and ductile. If dry, 
it adheres more or less to the tongue : if 
thrown into water, it gradually diffuses 
itself through it, and slowly separates from 
it. It does not usually effervesce with 
acids, unless a strong heat be applied, or 



9 

that it contains a few calcareous particles, 
or magnesia. If heated, it hardens and 
burns to a brick. 

It consists of argill and fine sand, usually 
of the silicious kind, in various propor- 
tions, and more or less -ferruginous. The 
argill forms generally from 20 to 75 per 
cwt. of the whole mass ; the sand and 
calx of iron the remainder. These are 
perfectly separable by boiling in strong 
vitrolic acid. 

Chalk, if not very impure, is of a white 
colour, moderate consistence, and dusty 
surface, stains the fingers, adheres slightly 
to the tongue, does not harden when heat- 
ed, but, on the contrary, in a strong heat 
burns to lime, and loses about four- tenths 
of its weight. It effervesces with acids, 
and dissolves almost entirely therein. I 
shall also add, that this solution is not dis- 
turbed by caustic volatile alkali, as this 
circumstance distinguishes it from magne- 
sia, — it promotes putrefaction. 

Sand, By this is meant small loose 
grains of great hardness, not cohering 
with water, nor softened by it. It is gene- 
rally of the silicious kind, and therefore 
insoluble in acids. 

Gravel differs from sand chiefiv in size : 
however stones cf a calcareous nature, 



10 

when small and rounded, are often com- 
prehended under that denomination. 

Loam denotes any soil moderately co- 
hesive : that is, less so than clay, and more 
so than loose chalk. By the author of the 
Body of Agriculture, it is said to be a clay 
mixed with sand. Doctor Hill defines it 
an earth composed of dissimilar particles, 
hard, stiff, dense, harsh, and rough to the 
touch, not easily ductile while moist, rea- 
dily diffusible in water, and composed of 
sand and a tough viscid clay. The defini- 
tion I have given seems most suited to the 
different species I shall now enumerate. 

Clayey Loam denotes a compound soil, 
moderately cohesive, in which the argilla- 
ceous ingredient predominates. Its cohe- 
rence is then greater than that of any other 
loam, but less than that of pure clay. 
The other ingredient is a coarse sand, with 
or without a small mixture of the calcare- 
ous ingredient. It is this which farmers 
generally call strong, stiff, cold, and heavy 
loam, in proportion as the clay abounds in 
it. 

Chalky Loam, This term indicates a 
loam formed of clay, coarse sand, and 
chalk ; in which, however, the calcareous 
ingredient or chalk much predominates. 
It is less cohesive than clayey loams. 

Sandy Loam denotes a loam in which 



11 

sand predominates : it is less coherent 
than either the abovementioned. Sand, 
partly coarse and partly fine, forms from 
80 to 90 per cent, of this compound. 

Gravelly Loam differs from the last only 
in containing a larger mixture of coarse 
sand, or pebbles. This and the two last 
are generally called, by farmers, light or 
hungry soils ; particularly when they 
have but little depth. 

Ferruginous Loam* or Till. This is 
generally of a dark brown, or reddish co- 
lour, and much harder than any of the pre- 
ceding : it consists of clay and calces of 
iron, more or less intimately mixed. It 
may be distinguished not only by its co- 
lour, but also by its superior weight : it 
sometimes effervesces with acids, and 
sometimes not ; when it does, much of the 
irony part may be separated, by pouring 
it, when well dried, into spirit of salt ; 
from which the iron may afterwards be 
separated by alkalis or chalk. 

Akin to this are certain vitriolic 

soils, which, when steeped in water, impart 
to it the power of reddening syrup of vio- 
lets. These are generally of a blue colour, 
but redden when heated. 

Boggy Soil or Bogs, consist chiefly of 
ligneous roots of decayed vegetables mix- 



12 

ed with earth, mostly argillaceous, and 
sand, and a coally substance derived from 
decayed vegetables. Of bogs there are 
two sorts : the black, which contain a 
larger proportion of clay and of roots 
more perfectly decayed, with mineral oil. 
In the red the roots seem less perfectly de- 
cayed, and to form the principal part. 

.Heathy Soil is that which is -naturally 
productive of heath. 



13 



SECTION IL 

OF MANURES. 

Manure denotes any substance or ope- 
ration by which a soil is improved. To 
improve a soil is to render it capable of 
producing corn, legumens, and the most 
useful grasses. 

The substances principally used as ma- 
nures, are chalk, lime, clay, sand, marl, 
gvpsum, ashes, stable-dung, mucks, farm- 
yard dung, pounded bones, sea- weeds, 
sweepings of ditches, old ditches. Other 
manures or top-dressings, as they are em- 
ployed chiefly to promote the growth of 
vegetables, and not merely with a view of 
improving the soil, I omit. 

The operations used to improve soils, 
are fallows, draining, paring and burning. 

Of chalk, clays, and sand, we have al- 
ready treated. 

Lime is a substance whose external 
characters and mode of production are 
well known. It differs from chalk and 
powdered limestone chiefly by the absence 
of fixed air, which is expelled from these 
during their calcination. This air it gree- 



14 

dily re-absorbs from the atmosphere, and all 
other bodies with which it comes in con- 
tact, and which can furnish it ; but it can- 
not unite with the air unless it is previ- 
ously moistened. 100 parts quick-lime 
absorb about 28 of water. It is soluble 
in about 700 parts of this fluid. To re- 
gain its full portion of air from the atmos- 
phere, it requires a year or more, if not 
purposely spread out : it resists putrefac- 
tion ; but with the assistance of moisture, 
it resolves organic substances into a mucus. 

Marl is of three sorts ; calcareous, ar- 
gillaceous, and siliciousor sandy. All are 
mixtures of mild calx (i. e. chalk) with 
clay, in such a manner as to fall to pieces 
by exposure to the atmosphere more or less 
readily. 

Calcareous Marl is that which is most 
commonly understood by the term Marl, 
without addition. It is generally of a yel- 
lowish white, or yellowish grey colour; 
rarely brown or lead coloured. It is sel- 
dom found on the surface of land, but 
commonly a few feet under it, and on the 
sides of hills, or rivers that flow through 
calcareous countries, or under turf in bogs. 
Frequently of a loose texture, sometimes 
moderately coherent ; rarely of a stony 
hardness, and hence called stone-marL 
Sometimes of a compact, sometimes of a 



15 

lamellar texture ; often so thin as to be 
called paper-marl. It often abounds with 
shells, and then is called shell-marl ; which 
is looked upon as the best sort. When in 
powder, it feels dry between the fingers ; 
put in water, it quickly falls to pieces or 
powder, and does not form a viscid mass. 
It chips and moulders by exposure to the 
air and moisture, sooner or later, accord- 
ing to its hardness and the proportion of 
its ingredients : if heated, it will not form 
a brick, but rather lime. It effervesces 
with all acids. It consists of from 33 to 
80 per cent, of mild calx, and from 66 to 
20 per cent, of clay. 

To find its composition; pour a few 
ounces of weak, but pure spirit of nitre, 
or common salt, into a Florence flask ; 
place them in a scale, and let them be ba- 
lanced ; then reduce a few ounces of dry 
marl into power, and let this powder be 
carefully and gradually thrown into the 
flask, until after repeated agitation no ef- 
fervescence is any longer perceived ; let 
the remainder of the powdered marl be 
then weighed, by which the quantity pro- 
jected will be known ; let the balance be 
then restored ; the difference of weight 
between the quantity projected and that 
requisite to restore the balance will dis- 



16 

cover the weight of air lost during effer- 
vescence ; if the loss amounts to 13 per 
cwt. of the quantity of marl projected, or 
from 13 to 32 per cwt. the marl essayed 
is calcareous marl. This experiment is 
decisive, when we are assured by the ex- 
ternal characters above mentioned, that 
the substance employed is marl of any 
kind ; otherwise some sorts of the sparry 
iron-ore may be mistaken for marl. The 
experiments to discover the argillaceous 
ingredient (being too difficult for farmers) 
I omit. The residue left after solution, be- 
ing well washed, will, when duly heated, 
generally harden into a brick. 

Argillaccou Marl contains from 68 to 
80 per cent, of clay, and consequently 
from 32 to 20 per cent, of aerated calx. 
Its colour is grey or brown, or reddish 
brown, or yellowish or bluish grey. It 
feeis more unctuous than the former, and 
adheres to the tongue : its hardness gene- 
rally much greater. In water it falls to 
pieces more slowly- and often into square 
pieces : it also more slowly moulders 
by exposure to the air and moisture, if of 
a loose consistence : it hardens when he. t- 
ed, and forms an imperfect brick, it effer- 
vesces with spirit of nitre or common salt, 
but frequently refuses to do so with vine- 



17 

gar. When dried and projected into spi- 
rit of nitre, in a Florence flask, with the 
attentions above-mentioned, it is found to 
lose from 8 to 10 per cwt. of its weight. 
Tne undissolved part, well washed, will, 
when duly heated, harden into a brick. 

Silicious, or Sandy Marls, are those 
whose clayey part contains an excess of 
sand : for, if treated with acids in the 
manner above-mentioned, the residuum, 
or clayey part, will be found to contain 
above 75 per cwt. of sand ; consequently 
chalk and sand are the predominant ingre- 
dients. 

The colour of this marl is brownish 
gray, or lead coloured : generally friable 
and flakey, but sometimes forms very hard 
lumps. It does not readily fall to pieces 
in water. It chips and moulders by ex- 
posure to the air and moisture, but slowly. 
It effervesces with acids ; but the resi- 
duum, after solution, will not form a 
brick. 

Limestone-Gravel. This is a marl 
mixed with large lumps of limestone. The 
marl may be either calcareous or argillace- 
ous ; but most commonly the former. 
The sandy part is also commonly calcare- 
ous. 

B 



18 

Gypsum is a compound of calcareous 
earth and vitrolic acid : it forms a distinct 
species of the calcareous genus of fossils : 
of which species there are six families. 

The general character of this species are, 

1. Solubility in about 500 times its 
weight of water, in the temperature of 
60°. 

2. Precipv ability therefrom by all mild 
alkalis, and also by caustic fixed, but not 
by caustic volatile alkali. 

3. Incffervescence with acids, if the 
gypsum be pure ; but some families of this 
species, being contaminated with mild 
calx, slightly effervesce. 

4. Insolubility , or nearly so in the ni- 
trous acid, in the usual temperature of the 
atmosphere. 

5. A specific gravity, reaching from, 
2,16 to 2,31. 

6. A degree of hardness, such as to ad- 
mit being scraped by the nail. 

7. When heated nearly to redness, it 
calcines ; and if then it be slightly sprink- 
led with water, it again concretes and har- 
dens. 

8. It promotes putrefaction in a high 
degree. 

Of the six families of this species I shall 
describe only one ; namely, that which 



19 

has been most advantageously employed 
as a manure. Descriptions of the other 
five should be found in treatises of mine- 
ralogy. It is called fibrous gypsum. 

Its colours are gray, yellowish or red- 
dish, or silvery white, or light red, or 
brownish yellow, or striped with one or 
more of these dark colours. It is compos- 
ed of fibres or striae, either straight or 
curved, parallel or converging to a com- 
mon centre, sometimes thick, sometimes 
fine and subtile, adhering to each other, 
and very brittle: its hardness such as to 
admit being scraped with the nail : com- 
monly semi-transparent ; in some, often 
in a hiffh decree. 

Ashes. Sifted coal-ashes, those of peat 
and white turf-ashes, have been found 
useful ; red turf ashes useless, and gene- 
rally hurtful. Wood- ashes have also been 
employed advantageously in many cases ; 
they contain either the four primitive 
earths, as Mr. Bergman asserts ; or cal- 
careous earth chiefly, according to Achard; 
or calcareous and magnesia, according to 
D^Arcet. They also contain some pro- 
portion of phosphorated selenite, i. e. cal- 
careous earth united to the phosphoric 
acid. Almost all contain also a small and 
variable proportion of common salt, Glau- 



20 

ber's salt, and terrene salts, which, when 
in a small dose, all accelerate putrefaction ; 
also small bits of charcoal. 

Charcoal is a substance well known ; it 
has frequently and successfully been used 
as a manure. 1st Young's Annals, 152, 
&c. 8cc. 

S ab-boilers Waste forms an excellent 
manure for some soils ; it contains, by 
Mr. Ruckert's Analysis, 57 per cwt. of 
mild calx, 1 1 of magnesia, 6 of argiii, and 
21 of silex 

Stable Dung. This is used either fresh 
or putrefied ; the first is called long, the 
other short dung ; it abounds in animal 
matter, easily runs into putrefaction, and 
when putrefied serves as a leaven to hasten 
the decay of other dead vegetable sub- 
stances ; its fermentation is promoted by 
frequent agitation and exposure to the air; 
yet it should be covered to prevent water 
from carrying ofT most of its important 
ingredients; or at least the water that im- 
bibes them should not be lost. 

Farm-yard Dung consists of various 
vegetables ; as straw, weeds, leaves, fern, 
&x. impregnated with animal matter ; it 
ferments more slowlv than the former ; 



21 

should be piled in heaps, and stirred, from 
time to time. Fern putrefies very slowly. 
The water that issues from it should be 
preserved. 

Some of these manures have been ana- 
Ivsed. 



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23 

Hence they should be applied, not in- 
discriminately, but according to circum- 
stances, to be indicated in the sequel. 

Pounded bones form also manure much 
used in the neighbourhood of great towns. 
They gradually deposit their oily part, 
which contains a large proportion of ani- 
mal coal which is extricated by putrefac- 
tion, and phosphorated calx. Hence Bone- 
ash is also useful. 

Sea-weed, particularly if mixed with 
earth, soon putrefies, and makes a good 
manure. 

Sweepings of Ditches abound with pu- 
trid matter from decayed vegetables, and 
hence form a manure. 

Old Ditches, exposing a large surface to 
vegetation, contain, when destroyed, a 
quantity of decayed vegetables, which 
putrefy and make a good manure ; but in 
this and the former case, it may be proper 
to distinguish of what soil they are com- 
posed, for reasons that will hereafter ap- 
pear. 

Fallowing, is the principal operation by 
which exhausted lands are restored to fer- 
tility ; its use seems to me to consist in ex- 
posing the roots of vegetables to decay, 
whereby food for a fresh growth is pre* 



24 

pared ; the atmosphere also deposits fix- 
ed air and carbonaceous substance on earth 
long exposed to it. 

Draining is an operation equally neces- 
sary and well known, on which no more 
need be said here. 

Paring and burning reduces the roots of 
vegetables to coal and ashes ; and thus 
prepares both a stimulant and nutriment 
for plants, as will be seen hereafter. 



25 



CHAP. II. 

OF THE FOOD OF PLANTS, AND THE COMPO- 
SITION OF FEE.TILE SOILS. 

HAVING, in the preceding chapter, 
expla'.ned the nature of the different soils 
known in agriculture, and of the different 
manures whose general utility has been 
ascertained by long experience, we are 
now to inquire whi< h of those manures 
are most advantageously applicable to 
each of those particular soils, and what 
are the causes of their beneficial effect in 
each particular instance. 

To proceed with order in this inquiry, 
we must observe, that the general effect 
expected from the application of manure 
is fertility; that is, the most copious pro- 
duction of corn and grasses ; and, since 
fertility is itself the result of the due ad- 
ministration of the food of those ves;eta- 
bles, we must first see what that food is, 
and of what ingredients a soil ought to be 
composed, in order to contain or adminis- 
ter it ; after which we shall indicate by 



26 

what manures each particular sort of soil 
is brought into a fertile state (which is the 
beneficial effect expected from them) and 
how in each particular case they contri- 
bute to the due adminstration of the vege- 
table food, which is the cause of their be- 
neficial effect. 



SECTION I. 

01' THE FOOD OF PLANTS. 

To discover the food of plants, particu- 
larly of those which form the object of 
our present inquiry, we must examine the 
nature and proportion of the substances in 
which they grow, and of those which they 
themselves contain : thus we shall be 
enabled to see which of the latter are de- 
rived from the former. 

First, All plants (except the subaque- 
ous) grow in a mixed earth, moistened 
with rain and dew, and exposed to the at- 
mosphere. If this earth be chemically 
examined, it will be found to consist of 
silicious, calcareous, and argillaceous par- 
ticles, often also of magnesia, in various 
proportions, a very considerable quantity 
of water, and some fixed air. The most 
f^f*j]p. also, contain n sm<n].l proportion or 



27 

oil, roots of decayed vegetables, a coaly 
substance arising from putrefaction, some 
traces of marine acid, and gypsum.- On 
the other hand, if vegetables be analysed, 
they will be found to contain a large pro- 
portion of water and charcoal ; also fat and 
essential oils, resins, gums, and vegetable 
acids : all which are reducible to water, 
pure air, inflammable air and charcoal : 
a small proportion of fixed alkali is also 
found, some neutral salts, most commonly 
gypsum, tartar, vitriolate, common salt, 
and salt of sylvius. In corn, and particu- 
larly wheat, phosphorated selenite is also 
found. 

Hence we see that, on the last analysis, 
the only substances common to the grow- 
ing vegetables and the soils in which they 
grow, are water, coal, different earths, and 
salts. These, therefore, are the true food 
of vegetables : to them we should also 
add fixed air, though, by reason of its de- 
composition, it may not be distinctly found 
in them, or at least not distinguishable 
from that newly formed during their de- 
composition. 

I shall now examine the separated func- 
tions of each of these ingredients. 

* Home, 15 Mem. D* Agriculture, Par. 1790. Rncyclo- 
paed. Vegetation, p. 'Tr - - 



28 



OF WATER. 



The agency of water in the process 
of vegetation, has never been doubted, 
though the manner in which it contributes 
to it has not, until of late, been distinctly 
perceived. Doctor Hales has shewn, that 
in the summer months a sun-flower weigh- 
ing three pounds avoirdupois, and regu- 
larly watered every day, passed through 
it, or perspired, 22 ounces each day ; 
that is, nearly half its weight. He also 
found that a cabbage plant, weighing 
1 lb. 9oz. sometimes perspired lib. 3 oz.; 
but at a medium about half its weight.* 
Doctor Woodward found that a sprig of 
common spearmint, a plant that thrives 
best in moist soils, weighingonly 28,25 grs, 
passed through it 3004 grs. in 77 days, 
between July and October ; that is, some- 
what more than its own weight each day. 
He did more ; for he found that in that 
space of time the plant increased 17 grs. 
in weight, and yet had no other food but 
pure rain water. But he also found that 
it increased more in weight when it lived 
on spring-water, and still more when its 
food was Thames water f. From whence 

* I rl.<! s, 9, 10,15. t 2Phi!.Tmni Abr.715. 



29 

we may deduce, that grasses and corn, 
during the time of their growth, absorb 
about one half their weight of water each 
day, if the weather be favourable. 

Secondly, that the water they thus pass 
nourishes them merely as water, without 
taking any foreign substance into the ac- 
count : for 3000 grs. of rain water, in 
Doctor Woodward's experiment, afford- 
ed an increase of 17 grains ; whereas, by 
MargraafF's experiments, 5760 grs. of that 
water contain only one third of a grain of 
earth*. But, 

Thirdly, It also follows, that water con- 
tributes still more to their nourishment 
when it conveys to them earthy and sa- 
line particles, as spring and Thames wa- 
ters do. 

The manner "hi which pure water con- 
tributes to the nourishment of plants, be- 
sides the service it renders them in distri- 
buting, the nutritive parts throughout their 
whole structure, and forming itself a con- 
stituent part of all of them, may be un- 
derstood from modern experiments. Doc- 
tor Ingenhouz and Mr. Senebier have 
shewn that the leaves of plants exposed 
to the sun produce pure air : now water 

* 2 Margr. 6, 70. 



30 

has of late been proved to contain about 
87 per cwt. of pure air, the remainder be- 
ing inflammable air. Water is then de- 
composed by the assistance of light with- 
in the vegetable ; its inflammable part is 
employed in the formation of oils, resins, 
gums, &x. its pure air is partly applied to 
the production of vegetable acids, and 
partly expelled as an excrement. 

Many, indeed, have asserted, that water 
is the sole food of vegetables ; and among 
the experiments adduced to prove it, that 
of Van Helmont, quoted by the illustrous 
Mr. Boyle*, is by far the most specious. 
He planted a trunk of willow, weighing 
51b. in an earthen vessel filled with earth 
dried in an oven, and then moistened with 
rain-water. This vessel, it appears, he 
sunk in the earth, and watered partly with 
rain-water, and occasionally with distilled. 
After five years he found the tree to weigh 
169 lb. and the earth in which it wus.plant- 
ed, being again dried, to have lost only 
2 oz. of its former weight, though the 
tree received an increase amounting to 
164 lb. 

Before I proceed to the explication of 
this experiment, I must remark some cir- 

V Shaw's Bovle, 2-10. 



eumstances attending it : First, that the 
weight of the earth contained in the ves- 
sel at the commencement and at the end of 
five years, could not be exactly compared, 
because the same degrees of desiccation 
could not be exactly ascertained, and be- 
cause many of the fibrillae of the roots of 
the tree must have remained in the earth 
after the tree was taken out of the vessel, 
and these must have prevented the true loss 
of earth from being perceived. Secondly, 
That the earthen vessel must have fre- 
quently absorbed water impregnated with 
whatever substance it might contain, from 
the surrounding earth in which it was in- 
serted ; for unglazed earthern vessels easi- 
ly transmit moisture. (1st Hales 5, and 
Tillet's Mem. Par. 1772, rage 298, 304, 
8vo.) Thirdly, As it appears that the pot 
was sunk in the earth, and received rain- 
water, it is probable that distilled water 
was seldom used. 

These circumstances being considered, 
it will easily be made to appear that the 
rain-water, absorbed by the tree, contain- 
ed as much earth as the tree can be sup- 
posed to contain. 

First, The willow increased in weight 
164 lb. in five years ; that is, at the rate of 
2,7 lb. nearly per month ; and it being an 



32 

aquatic, it cannot be supposed to pass less 
than its own weight of water each day 
during the six vegetating months. In the 
first mouth, therefore, it absorbed and 
passed 5x30-= 150 lb. and as each pound 
of rain-water contains ■} gr. of earth, 50 
grains or earth must have been deposited 
in the plant ; and allowing no more than 
50 grains for the deposit of each of the six 
months, we shall have 50x6=300 for 
the deposit of the first year : but at the 
end of the first year the plant gains an ac- 
cession of the 321b. therefore, in each of 
the six summer months of the succeeding 
year, it passes 37x30=1110 lb. of water, 
and receives a deposit of 370 grains ; and 
at the end of the second year the deposit 
amounts to 2220 grains. At the com- 
mencement of the third year, the tree 
gaining a farther accession of 32 lb. must 
weigh 69 lb. and pass in each of the sum- 
mer months 69x30=2070 lb. of water, 
and receive a deposit of 690 grs. which 
multiplied into 6— 4140 grains. At the 
commencement of the fourth year, the 
tree still gaining 32 lb. must weigh 1011b; 
and if it passes 101x30 in each of the 
summer months, it must gain a deposit in 
each of 1010 grs. of earth, and at the end 
of the vear, 6060. 



At the commencement of the fifth year 
it weighs 133 lb. and gains at the end of 
the six months 23940 grains of earth. 
The quantities of earth deposited each 
year exceed 5 lb. avoirdupois, a quantity 
equal to that which 169 lb. of willow can 
be supposed to contain ; for the commis- 
sioners employed to inspect the fabrica- 
tion of saltpetre in France, having exam- 
ined the quantities of ashes afforded by 
trees of various kinds, found that 1000 lb. 
of sallow, a tree much resembling the 
willow, afforded 28 lb. of ashes, and con- 
sequently 169 lb. should produce 4,7. 1 
do not give this calculation, however, as 
rigorously exact. It is certain, that if the 
deposit left at the end of every month 
were exactly taken, the total would ex- 
ceed the quantity just mentioned ; but that, 
found even by this rude mode, sufficiently 
proves that water conveys a portion of 
earth into vegetables equal to any that the 
experiments hitherto made can prove to 
exist in them. 

As to the coal, or carbonaceous princi- 
ple, which this willow must also have 
contained, it is probable that much of it 
existed in the earth in which the willow 
grew. Some is contained in all moulds or 

C 



34 

vegetable earth ; and as we are not told 
what sort of earth Van Helmont used, we 
may well suppose it was good vegetable 
earth, its quantity amounting to 200 lb. 
This principle may also have been contain- 
ed in the water, for the purest rain-water 
contains some oleaginous particles, though 
in an exceeding small proportion, as Mr. 
Margraaff has observed* ; and all oil con- 
tains coal. Some also may have pas- 
sed from the surrounding vegetable earth 
through the pores of the earthen vessel. 
All the other experiments, adduced to 
prove that water is the sole food of plants, 
may be explained in the same manner. 
Grains of wheat have been made to grow 
on cotton moistened with water ; each 
produced an ear, but that ear contained but 
one grain |- Here the carbonaceous sub- 
stance was derived from the grain, and 
afterwards diffused and transported through 
the whole plant by the water absorbed ; 
for it must be observed that grain, like an 
egg, contains much of the nourishment of 
ks future offspring. It is thus that tulips, 
hyacinths, and other plants, expand and 
grow in mere water. 

The earth contained in rain-water is 

* 2d Margr. 15,90. f 2d Young's Annals, 487. 



35 

united partly with the nitrous and marine 
acids, as Margraaff has shewn, but far the 
greater part only with fixed air ; for the 
feeble traces of the two former acids could 
not hold in solution the 100 grains of earth 
which he found in 300 lb. of rain-water. 
By far the greatest proportion of vege- 
table substances consist of water. Accor- 
ding to Mr. Young and Ruckert, grass 
loses about 2-thirds of its weight on be- 
in^ dried into hay*. Dr. Hales found a 
sun-flowerplant, which weighed 48 ounces, 
to lose 36 ounces by drying in the air dur- 
ing thirty daysj, and consequently to 
have lost 3 -fourths of its weight. Even 
vegetables to appearance thoroughly dry, 
contain from 3 -fifths to 3 -fourths of their 
weight of waterj. This water is not all 
in a liquid state, but, by the loss of much 
of its specific heat, is in a great measure 
solidified. 



* 2d Young's Ann. 26. 2d Ruck. 139: 

t 1st Hales, 8. 

t Ruckert, 23. Sencb. Encyclop. Vegetation. 5i, 



36 



OF COAL, OR THE CARBONIC SUBSTANCE. 

To Mr. Hassenfraz we owe the dis- 
covery, that coal is an essential ingredi- 
ent in the food of all vegetables. Though 
higherto little attended to, it appears to be 
one of the primaeval principles, as ancient 
as the present constitution of our globe : 
for it is found in fixed air, of which it 
constitutes above one-fourth part ; and 
fixed air exists in lime-stones and other 
substances, which date from the first ori- 
gin of things. 

Coal not only forms the residuum of all 
vegetable substances that have undergone 
a blow and smothered combustion, that is, 
• to which the free access of air has been 
prevented, but also of all putrid vegetable 
and animal bodies : hence it is found in 
vegetable and animal manures that have 
undergone putrefaction, and is the true 
basis of their ameliorating powers : if the 
water that passes through a putrefying 
dunghill be examined, it will be found of 
a brown colour ; and if subjected to eva- 
poration, the principal part of the residuum 



37 

will be found to consist of coal*. All soils 
steeped in water communicate the same 
colour to it in proportion to their fertility; 
and this water being evaporated, leaves 
also a coal, as Mr. Hassenfraz and Four- 
croy attestf. They also observed, that 
shavings of wood being left in a moist 
place for nine or ten months, began to re- 
ceive the fermentative motion, and being 
then spread on land, putrefied after some 
time, and proved an excellent manurej. 
Coal, however, cannot produce its benefi- 
cial effects but in as much as it is soluble 
in water. The means of rendering it so- 
luble are not as yet well ascertained ; ne- 
vertheless, it is even now used as a ma- 
nure, and with good effect^. In truth, 
the fertilizing power of putrid animal and 
vegetable substances were fully known 
even in the remotest ages, but most specu- 
latists have hitherto attributed them to the 
oleaginous, mucilaginous, or saline parti- 
cles then developed, forgetting that land is 
fertilized by paring and burning, though 
the oleaginous and mucilaginous pai tides 
are thereby consumed or reduced to a coal, 
and that the quantity of mucilage, oil or 
salt in fertile land is so small, that it could 

* H Ann. Gliym. 55. f Ibid. 

-t Ibid. § Young's Annals. 



38 

not contribute the 1000th part of the 
weight of any vegetable ; whereas coal is 
supplied not only by the land, but also by 
the fixed air combined with the earths, 
and also by that which is constantly set 
loose by various processes, and soon pre- 
cipitates by the superiority of its specific 
gravity, and is then condensed in, or me- 
chanically absorbed by, soils, or contained 
in dew. Lands which contain iron in a 
semicalcined state, are thereby enabled to 
decompose fixed air, the iron> by the help 
of water, gradually attracting the pure air, 
which enters into the composition of fixed 
air, as Mr. Gaclolin has shewn* : a disco- 
very which appears to me among the most 
important of these later times ; but these 
calces of iron may again be restored to 
their former state by union with oleagin- 
ous substances, as Mr. Beaume has no- 
ticed ; and this is one of the benefits re- 
sulting from the application of dung be- 
fore it has fully putrefiedf. Hence we 
may understand how soils become effect- 
ed and exhausted, this effect arising, in 
great measure, from the gradual loss of 
the carbonic principle deposited by vege- 

* 1st Chym. Ann. 1791, 53. 

f The affinities of coal and iron to pure air 3 vary with the 
temperature- 



39 

table and animal manures, and from them 
passing into the growing vegetables ; and 
also from the loss of the fixed air contain- 
ed in the argillaceous part of the soil, 
which is decomposed by vegetables ; and 
from the calcination of the ferruginous 
particles contained in the soil. I say 
in great measure, because other causes 
contribute to the diminution of fertility ; 
which shall presently be mentioned. Hence, 
also, we see why lands pastured remain 
longer fertile than those whose vegetable 
crop is carried off, as much of the carbo- 
naceous principle is restored by the ex- 
crements of the pasturing animals : why 
some crops exhaust more than others ; 
because corn, and particularly wheat, con- 
tains more of the carbonic principle than 
grasses, and very little of its exuviae are 
left behind : why fallows are of some 
use ; as the putrefaction of the roots of 
weeds and the absorption of fixed air by 
clays, are thereby promoted: why vege- 
tables thrive most in the vicinity of towns; 
because the carbonic principle is copious- 
ly dispersed by the smoke of the vari- 
ous combustibles consumed in inhabited 
places : why soot is so powerful a ma- 
nure : why burning the clods of grassy 
land contributes so much to its fertility 



40 

and then only when the fire is smothered 
and coal produced ; besides many other 
agricultural phenomena, too tedious to re- 
late : but I must not omit that the phos- 
phoric acid is found in coal ; and this en- 
ters into the composition of many vegeta- 
bles. 

The quantity of coal in vegetables is 
various, according to their various species, 
age, and degrees of perfection : wood and 
corn contain most, grasses least. Weig- 
leb found dry beech- wood to contain one 
fifth of its weight of coal*. Westrumb 
found trifolium pratense, a sort of clover, 
to contain about one seventh. Hence, 
after water, it is the most copious ingre- 
dient in vegetables. 



Or EARTHS. 

The next most important ingredient to 
the nourishment of plants is earth : and 
of the different earths the calcareous seems 
the most necessary, as it is contained in 
rain-water : and, absolutely speaking, ma- 
ny plants ma}^ grow without imbibing any 
other. Mr. Tillet found corn would grow 

* Uber die alkalis, p. 76. 



41 

in pounded glass* ; Mr. Succow in pound- 
ed fluor spar, or ponderous spar, or gyp- 
sumf : but Tillet owns it grew very ill ; 
and Hassenfraz, who repeated this experi- 
ment, found it scarcely grow at all when 
the glass or sand were contained in pots 
that had no hole in the bottom, through 
which other nutritive matter might be 
conveyed. It is certain, at least, from 
common experience, that neither grasses 
nor corn grow well either in mere clay, 
sand, or chalk ; and that in vegetables 
that grow most vigorously, and in a pro- 
per soil, three or four of the simple earths 
are found. Mr. Bergman, on the other 
hand, assures us he extracted the four 
earths, the silicious, argillaceous, calcare- 
ous, and muriatic, in different proportions 
from the different sorts of cornt. Mr. 
Ruckert, who has analysed most species 
of corn and grasses, found also the four 
above-mentioned earths in various pro- 
portions in all of them. Of his analysis 
I shall here give a specimen, comprehend- 
ing, however, the calcareous and muria- 
tic in the same column, as this last scarce 
ly deserves particular notice : 

* Mem. par. 1772, 301, 8vo. 

t 1st C!»vn». Ann. 1784. 

{ 5 Berg-man, 94, y& Scheie* Wurl-s, sjc. 172. 

D 



42 



One hundred parts 


of 


the lixiviated 


ashes of 












contained < 


if Silex. Calx. 


Argill. 


Wheat - - - 


f - 48pts. 


37 


15 


Oats 


1 - 68 




26 


6 


Barley - - - 


- 69 




16 


15 


Bere - - - -< 


' - 65 




25 


10 


Rye 


- 63 




21 


16 


Potatoes - 


4 




66 


30 


Red Clover 


L - 37 




33 


30 



Mr. Ruckert is persuaded that earth 
and water, in proper proportions, form the 
sole nutriment of plants ; but Mr. Gio- 
bert has clearly shewn the contrary ; for, 
having mixed pure earth of alum, silex, 
calcareous earth, and magnesia, in vari- 
ous proportions, and moistened them with 
water, he found that no grain would grow 
in them ; but when they were moistened 
with water from a dunghill, corn grew 
in them prosperously*. Hence the ne- 
cessity of the carbonic principle is appa- 
rent. 

The absolute quantity of earth in ve- 
getables is very small. Dr. Watson in- 
forms us that 106 avoirdupois pound 
= 1696 ozs. of oak, being carefully burn- 
ed, left but 19 ozs. of ashes ; and from 

* Encyclop. Vegetation, 274. 



43 

these we must deduct 1,5 for salt, then 
the earthy part amounts only to 17,5 ; 
that is, little more than one per cwt. The 
commissioners appointed to inspect the 
saltpetre manufactory, found nearly the 
same result ; namely, 1,2 per cwt. in 
beech 0,453, and in fir only 0,003. Hence 
we need not wonder at trees growing 
among rocks where scarce any earth is to 
he seen : but in the stalks of Turkey- 
wheat, or maize, they found 7 per cwt. 
of earth, in sun-flower plant 3,7* ; so that, 
upon the w T hole, weeds and culmiferous 
plants contain more earth than trees do. 
Mr. Westrumb found tri folium prat ens e 
to contain about 4,7 per cwt. of earth, of 
which 2 per cwt. was mild calx, nearly 
2 more silex, 0,7 argill, together with a 
small proportion of phosphorated iron, 
calx of iron, and manganesef. 

Since plants derive some proportion of 
earth from the soil on which they grow, 
we cannot be surpised that these soils 
should, at length, be exhausted by crops 
that are carried off; such as those of corn 
and hay, particularly the former : even 
lands pastured must at last be exhausted, 
as the excrements of animals do not re- 

* See 3 Trans. Roy?l Irish Academy, 
f Isi Chvm. Ann. 187. 



44 

store the exact quantity that the animals 
have consumed ; and hence the utility of 
mucks, as the restoration is performed by 
more animals than have been employed in 
the consumption. Hence also a succes- 
sion of different crops injures land less 
than a succession ci crops of the same 
kind, as different proportions of the differ- 
ent earths are taken up by the different 
vegetables. Finally, we may hence de- 
rive the utility of marling land as the de- 
ficient earths are thereby replaced. This 
subject admits of more precision than has 
been hitherto imagined, and may even be 
subjected to calculation. The absolute 
quantity and relative proportions of the 
various earths in an acre of land may be 
determined, so ma} that in the crops of 
differ ent vegetables ; and by comparing 
both, the time also may be found in which 
the land must be exhausted, unless reno- 
vated bv various manures : thus the ne- 
cessity of marling. The kind of marl or 
other manures, and the quantity necessa- 
ry to an acre of land, may be very nearly 
ascertained. 

Earths cannot enter into plants but in a 
state of solution, or at least only when sus- 
pended in water in a state of division as 
minute as if they had been really dissolv • 



45 

ed. That silicious earth may be suspend- 
ed in such a state of division appears from 
various experiments, particularl) those of 
Mr. Bergman, who found it thus diffused 
in the purest waters of Upsal ; and it is 
equally certain that it enters copiously into 
vegetables. Both his experiments, and 
especially those of Mr. Macie, establish 
this point beyond contradiction*. Argil- 
laceous earth may also be so finely diffused 
as to pass through the best filters ; so alsa 
may calx, as appears from the quantity 
Margraaff found in the purest rainwater. 
This earth is even soluble by means of an 
excess of fixed air in about 1500 times its 
weight of water. It may also be, and 
most frequently is converted into gypsum 
by the vitriolic acid which most clays con- 
tain, as Mr. Morveau has shewnf , and 
then it is soluble in 500 times its weight 
of water. 

Vegetables not only require food, but 
also that this food be duly administered to 
them ; a surfeit is as fatal to them as ab- 
solute privation. Doctor Hales observed r 
that a young pear tree, whose roots were 
set in water, absorbed a smaller quantity 
of it every day, the sap-vessels being sa 

* Phil. Trans. 1791. 

f 1st Encyclop. Cbyra. 123. 



4& 

tu rated and clogged by it ; and Mr. Mif- 
ler found that too much water rotted the 
young fibres of the roots as fast as they 
pushed out*. Saturated solutions of dung 
appeared to Mr. Du Hamel equally hurt- 
fulf. Now the preservation and due ad- 
minstration of this liquid food is effected 
by due proportions of the simple earths 
and their loose or condensed state. Their 
situation in other respects being the same, 
those thnt abound in f he argillaceous prin- 
ciple are the most retentive of water ; 
those that abound in the coarse silicious, 
least ; the calcareous being intermediate 
between both ; various species of vegeta- 
bles requiring various quantities of water 
and other food : hence it is that every 
sort of soil bears vegetables peculiarly 
adapted to it, while others do not grow at 
all, or but. ill in it. By the experiments 
of Mr. Bergman, we find that 

Argil! takes up 2,5 times its weight of 
water when saturated so as to let none 
drop. 



Magnesia - 


1,05 


Chalk - - 


0, 5 


Silicious Sand - 


0,25 


* 1st Hales, 17. 




t Mem. Par. 1743. 





47 



FIXED AIR. 



That plants do not thrive, but most fre- 
quently perish, when surrounded by an 
atmosphere of fixed air, has long been ob- 
served by that great explorer of the 
most hidden processes of nature, Doctor 
Priestly ; but that fixed air imbibed by 
the roots is favourable to their growth, 
seems well established by the experi- 
ments of Doctor Perceval, of Manchester, 
and fully confirmed by those of Mr. 
Ruckert. This last-mentioned philoso- 
pher planted two beans in pots of equal 
dimensions filled with garden-mould. The 
one was watered almost daily with distil- 
led, the other with water impregnated with 
fixed air, in the proportion of half a cu- 
bic inch to an ounce of water ; both were 
exposed to all the influences of the atmos- 
phere, except rain. The bean treated 
with aerated water appeared over ground 
nine days sooner than that moistened with 
distilled water, and produced 25 beans ; 
whereas the other pot produced only 15. 
The same experiment was made on stock- 
July-flowers, and other plants, with equal 



48 

success*. The manner in which fixed air 
acts in promoting vegetation, seems well 
explained by Mr. Senebier : he first dis- 
covered that fresh leaves exposed to the 
sun in spring- water, or water slightly im- 
pregnated with fixed air, always produce 
pure air as long as this impregnation lasts ; 
but as soon as it is exhausted, or if the 
leaves be placed in water out of which 
this air has u een expelled by boiling, they 
no longer afford pure airf : from whence 
he infers that fixed air is decomposed, its 
carbonic principle retained by the plant, 
and its pure air expelled. It appears to 
me, also, by acting as a stimulant, to help 
the decomposition of water. Mr. Has- 
senfraz, indeed, denies its decomposition ; 
but his arguments do not appear to me 
conclusive, for reasons too tedious and 
technical to mention here. The vitriolic 
acid contained in various clavs brought into 
multiplied contact with calcareous earth 
bv the agitation of soils in agricultural 
operations, and the motion of the roots, 
gradually sets loose the fixed ah* contain- 
ed in this last-mentioned earth ; that por- 
tion a'so of this earth, which is by water 
introduced into the plant, is decomposed, 

* 21 Chym. Ann. 1788, 399. 

f S;:.- ['influence Je iu Lumiere, vk 41 Rosier, 206. 



49 

and its air set loose by the vegetable acids 
of the plant. 

OF SALINE SUBSTANCES. 

Saline substances (gypsum and phos- 
phorated calx excepted) seem to serve ve- 
getables (as they do animals) rather as a 
condimentum, or promoter of digestion, 
than as a. pabulum. This idea is suggested 
by the smallness of their quantity, and the 
offices they are known to perform. Their 
quantity is always smaller than that of 
earth ; and this we have already seen to 
be exceeding small. 

Thus one thousand pound of lb. 

Oak gives of saline matter only 1,5 
Elm -• - - - 3,9 

Beech - 1,27 

Fir - - - - 0,45 

Vine branches - - 5,5 

Fern - - 4,25 

Stalks of Turkey wheat 17,5 

Wormwood - - - 73 
Fumitory ... 79 

Trifolium pratense - - 0,78 
Vetches* - - - 27,5 

Beans with their stalks* - 20 

* 3 Ruck. 49. 

D 



50 

In all the experiments hitherto made, 
the proportion of saline matter to the ear- 
thy has been found smallest in woods. In 
other plants, generally as 1 to 1,3, 1,5, or 
2 ; however, Mr. Ruckert has marked 
some exceptions, which I shall mention as 
worthy of notice. 



PROPORTION OF SALINE SUBSTANCES TO THF 
EARTHY. 



In Hemp - 


as 


1 to 8. 


Flax 


- 


1 to 1,7 nearly 


Parsnips 


. 


1,1 to 1. 


Potatoes 


. 


1 to 1,3 


Turnips 
Wheat 


- 


1 to 3,33 
1 to 3. 


Rye 

Oats 


- 


1 to 8. 
1 to 8. 



These proportions have some analogy 
with the quantity and sort of manure pro- 
per to be employed in the cultivation of 
these plants and the succession of crops. 
But I shall enter no farther into this sub- 
ject as it would lead me too far from the 
present object of enquiry. 

The salts generally extracted from the 
ashes of vegetables, are tartar vitriolate, 



51 

Glauber's salt, common salt, salt of Syl- 
vias, gypsum, phosphorated calx, and 
fixed alkalis. 

Alkalis seems to be the product of the 
vegetable process, for either none or scarce 
any is found in the soils, or in rain-water, 
while in the vegetable they are, most prob- 
ably, neutralized, partly by vegetable acids 
which are decomposed in the process of 
combustion, and partly by the vitriolic and 
marine acids. Westrumb found tartar 
vitriolate and digestive salts in the juices 
of trifolium. 

Gypsum probably exists in greater quan- 
tity in plants than it appears to amount to 
after combustion and lixiviation ; much of 
it must be decomposed during the combus- 
tion, and still more during lixiviation, by 
the alkalis existing in the solution. Thus 
the apparent quantity of tartar vitriolate is 
increased. 

Phosphorated Calx is found in greatest 
quantity in wheat, where it contributes to 
the formation of the animal gluten. Hence 
in rainy years the quantity of gluten in 
wheat has been observed to be smaller.* 
Hence the excellence of bone- ashes as a 
manure for wheat ; and hence wheat 

* 2d Witwer's Dissertations, 103. 



52 

succeeds best after clover, if the clover be 
fed off, but not if it be mowed,* as much 
of the phosphoric acid is communicated by 
the dung of animals. 

The chief use of tartar vitriolate seems to 
be, that it promotes the decomposition of 
water, as Mr. Senebierhas observedf. 

* 2d Young's Annals, 36, 37. 
t Sur ia Lumiere, p. 130- 



53 



SECTION IL 

OF THE CONSTITUTION OF FERTILE SOILS, AND" 
THE METHOD OF ESTIMATING THEIR FER- 
TILITY. 

The most fertile soil is that which con- 
tains the greatest quantity of the food of 
those vegetables that nourish men and use- 
ful animals, and administers it to them 
with due economy. 

The first essential requisite, therefore, 
to a fruitful soil is, that it contain a suf- 
ficient quantity of the three or four simple 
earths above mentioned, and of the solu- 
ble carbonaceous principle. The other 
requisites are, that the proportion of each t 
and general texture of the soil be such as 
to enable it to admit and retain as much 
water as is necessary to vegetation, and 
no more. 

Now we have already seen, that the re- 
tentive powers of moisture are very differ- 
ent in the simple earths : therefore the 
proportions in which the fertility of a soil 
requires them to be mixed, must be dif- 
ferent in climates and countries that differ 



54 

considerably in moisture : in the drier, 
they must be such as are most retentive : 
in the moister, such as suffer it to pass 
or evaporate more easily. 

The same remark extends to situation. 
Lands on a plain should be so constituted 
as to be less retentive of water than those 
situated on a declivity ; as is very evi- 
dent. 

So lands that have a retentive or im- 
permeable sub- soil, should be differently 
constituted from those that have one less 
retentive or more permeable. The time 
of the year in which rain most abundantly 
falls may also be worthy of notice. 

These circumstances must, undoubt- 
edly, modify the conclusions that may be 
drawn from the experiments I shall now 
relate. 



ANALYSIS OF A FERTILE SOIL IN A VERY RAINY 
CLIMATE. 

Mr. Giobert has communicated to the 
public, the analysis of a fertile soil in the 
vicinity of Turin, where it rains yearly 
above 40 inches on the square foot. He 
found 1 lb of it to contain from 20 to 30 
grains of extractive matter which flamed 



55 

and burned, and therefore was a coal solu- 
ble in water ; 26 lb. of it contained 1808 
grains of water. The simple earths were 
in the following proportion per cwt.* 

Silex, from — 77 to 79 

Argill 9 — 14 

Calx 5 — jo 

Hence the pound should contain,! 

grs. 

Carbonic matter — 25 

Water — — — 70 

Silex, from 4362 to 4475 

Argill — 509 — 793 

Calx — 283 — 679 

He also found it to contain a great deal 
of air (about 19 grains) of which one-third 
was fixed, and the remainder heavy inflam- 
mable air : but no volatile alkali. 

The weight of a cubic foot of this soil 
does not appear, nor is its specific gravity 
given ; hence neither its texture, nor the 
quantity of each ingredient, can be di- 
rectly ascertained; yet, from the necessity 

* Enc> clop. Vegetation 276. 

t The Turin medicin:-! pound is divided like the trov &r>d 
contains the same number of grains. " 



56 

of its being, in some degree, open, and the 
weights of good soil found by Mr. Fa- 
broni,* I conclude its specific gravity can- 
not exceed 1,58: then a cubic foot of it 
should weigh about 120 lb. troy, or 100 
avordupois. 

In less fertile soils, Mr. Giobert found 
the proportions of 

Silex, from 48 to 80 
Argill — 7—22 

Calx — 6 — 11 

Hence the troy pound contained, of 

Silex, from 2716 to 4528 
Argill — 396—1245 
Caix — 339 — 662 

allowing 100 grains for moisture, as either 
the calx or argill exceeds the proportions in 
more fertile lands. 

The specific gravity of these soils is not 
given ; but it probably exceeds or falls short 
of that of the more fertile soils. 

* 8 Young's Annals, 174. 



57 



IN BARREN SOILS, 



The proportions of Silex, from 42 to 8S 

Argill — 20—30 
Calx — 4—20 

Hence the troy pound contained, allow- 
ing for water 120 grains, 

Silex, from 2368 to 4963 
Argill — 1128 — 162 
Calx — 225 — 620 



The specific gravity of these soils is not 
given ; but it probably is either much 
above or much below that of the former, 
as they are either too close or too open. 
Mr. Fabroni found that of barren sandy 
land 2,21. 

Note also, that if the proportion of 
water be different from that here suppos- 
ed, the contents of the troy pound will 
also be different ; but may be easily recti- 
fied. 

ANALYSIS OF A FERTILE SOIL, WHERE THE FALL 
OF RAIN IS 24 INCHES. 

Mr. Bergman found that a fertile soil, 
situated on a plain, where the yearly fall of 

E 



5$ 

rain amounts to 15 Swedish (that is 23,9 
English) inches contained four parts clay, 
three of silicious sand, two of calcareous 
earth, and one of magnesia (in all ten parts;) 
but the last not being of absolute necessity 
may be annexed to the calcareous. 

The composition of the clay he does not 
expressly mention, but we may suppose it 
such as most frequently occurs, contain- 
ing 66 per cwt. of fine silicious sand, and 
34 of mere argill : consequently 0,40 of it 
contain nearly 0, 14 of mere argill: and 0,26 
of fine silicious sand. 

The silicious sand, mentioned by Mr. 
Bergman, is what we call gravel (consisting 
of stone from the size of a pea, or less, to 
that of a nut ; ) and thus he himself explains 
it.* This amounts to 30 per cwt. 

Hence we may state the proportions thus : 

Coarse Silex 30 

Finer — - - - 26 

— t — 56 parts 
Argill — - - - 14 

Calx — - - - 30 



100 



* 5 Bergman, 10?, 103. 



59 



The use of the gravel is to keep the soil 
open and loose : a circumstance absolute- 
ly necessary, as I have before observed. 

The specific gravity is not given, but 
should not much exceed, I suppose, 1,600. 
Muschenbroek found that of garden-mould 
1,630. The carbonic matter was not 
known to Mr. Bergman. 

The proportion in a troy pound, sup- 
posing the quantity of water and coal not 
to exceed 100 grains, stands thus, omit- 
ting fractions : 



Gravel 
Fine Sand - 


1698 
1471 

3169 


A r gill - - 
Calx - - 


792 
1698 



Here we see the quantity of calx much 
greater than in the soil of Turin, where the 
fall of rain is greater: for in the drier climates 
there is a necessity to retain the rain, and the 
argill if increased would retain it too long 
and too much ; and, besides enters very 
sparingly into the constitution of plants. 

The following experiments were made 
by Mr. Tillet/at Paris, where the fall of 
rain amounts to 20 inches at an average* 



60 

He filled with mixtures of different 
earths a number of pots twelve inches in 
diameter at the top, ten at the bottom, and 
seven or eight deep. It appears also, that 
they were so porous as to absorb moisture, 
and that they were perforated at the bot- 
tom. These he buried up to the surface 
in a garden, sowed in each some grains of 
wheat, and then abandoned them to na- 
ture. 

FERTILE MIXTURES. 

1st. The first mixture he found fertile, 
consisted of three-eighths of the potters 
clay of Gentilly=0,375, three-eighths of 
the parings of lime-stone, and two-eighths 
of river sand = 0,25. In this, the corn 
grew very well for three years ; that is, as 
long as the experiment lasted. 

As potters clay is not pure argill, and 
as Mr. Tillet does not mention the pro- 
portion the mere argillaceous part bore 
to the silicious, I must supply this defect, 
by supposing this clay to contain near one 
half of its weight of pure argill, as it is clay 
of this sort that potters generally chuse ; 
and that of Gentilly is esteemed one of the 
best. Both the clay and lime-stone, he 
tells us, were pulverized, that they might 



61 



more exactly incorporate when mixed. 
Then the centesimal proportions will 
stand thus : 

Coarse Silex . . 25 



Finer — 



21 
■46 



£f U - - 16,5 

Calx _ -37,5 



100 



The quantities in the troy pound, sup- 
posing the water, &c. to amount to 100 
grains, are, 



Coarse Sand 
Finer — 



Argill 
Calx 




5659 



2< 



Id. This contained two-eighths of pot 
ters clay, three-eighths parings of lime- 



62 

stone, and three-eighths coarse sand, 
The centesimal proportions are, 

Coarse Sand - - 37,5 
Finer — - - 14 



51,5 

Argill — 11 

Calx — - - 37,5 



100 



In the troy pound, supposing the quan- 
tity of water to amount to 100 grains, the 
quantities of the three earths will be, 

Coarse Silex - - 2122 
Finer — - - 792 

2914 

Argill — - - 622 

Calx — - - 2122 



5658 



Hence we see that in the drier coun- 
tries, where the fall of rain is but 20 in- 
ches, the soil, to be fertile, must be closer, 
and the quantity of calcareous earth much 
increased, and that of the silicious much 



03 

diminished. Thus, in the climate of 
Turin, where the fall of rain exceeds 40 
inches, the proportion of silicious earth is 
from 77 to 80 per cwt. and that of calca- 
reous, from 9 to 14, to suffer this excess 
of rain more easily to evaporate. In the 
climate of Upsel, where the fall of rain is 
24 inches, the proportion of silex is only 
56 per cwt. but that of calx is 30 ; and in 
the climate of Paris, which is still drier, 
the proportion of silex is only from 46 to 
51, and that of calx 37,5 per cwt. and 
hence we may perceive the necessity of at- 
tending to the average quantity of rain to 
judge of the proper constitution of fertile 
lands on fixed principles. The quantity 
of rain differs much in different parts of 
the same kingdom ; but in general in Ire- 
land, I believe it to be between 24 and 28 
inches on an average. 

In the two last mixtures the proportions 
vary considerably : The first may serve as 
a model for the heavier soils, and the se- 
cond for the lighter. In these and the fol- 
lowing experiments, the carbonic princi- 
ple seems to have been extracted from the 
surrounding garden-mould with which the 
pots communicated, by means of their per- 
foration, at bottom. 



64 



BARREN MIXTURES. 



FIRST. 



Mr. Tillet, in his sixth and eighth ex- 
periments, mixed three-eighths of potters 
clay with three- eighths of parings of lime- 
stone and two-eighths of fine sand ; the 
only difference between this mixture and 
that of the first experiment was, that in the 
first experiment coarse sand was used, 
and in this fine, yet the former was fruit- 
ful in the highest degree ; but in this the 
grain prospered indeed the first year, but 
sickened in the second, and failed in the 
third : the proportions have been already 
staled. Here we have a clear proof of the 
necessity of an open texture in soils, with- 
out which the best proportions are use- 
less. 



SECOND. 



In his thirteenth experiment he employ- 
ed a mixture of two- eighths potters clay, 
four- eighths coarse sand, and two-eighths 
marl. The corn grew well the first year. 
poorly the second, and decayed the third. 



65 

The composition of the marl is not men- 
tioned ; but supposing it to contain 70 per 
cwt. of calx, and 30 of clay, of which the 
one-half is argill, it would form one of the 
richest sorts of marls. The centesimal 
proportions of this mixture should he, 

Silex . - 50x14=64 

Argill \- - ll x 8 = 19 

Calx - 17 



100 



And in. the troy pound, supposing the 
water, &c. to amount to 100 grains, the 
quantities will be, 

Silex - . 3622 

Argill - •- 1075 

Calx - . 962 



5659 



The sterility of this mixture seems to 
proceed from a defect of calcareous earth, 
if we suppose the marl poorer in thai 
earth, the defect will be still greater 1 . The 
retentive powers of the different earths 



66 

with respect to water, being expressed by 
the quantities which each can retain with- 
out suffering any to drop, as above said, 
and the quantities retained by the mixed 
mass of these earths being proportional 
to the respective quantities of each, it 
should seem that in fertile soils, where the 
fall of rain is from 20 to 50 inches, this 
power should not exceed 70, nor fall short 
of 50 per cent. It were of great conse- 
quence to settle this point with precision ; 
but to do this would require more nume- 
rous experiments. To explain my mean- 
ing, I shall give one example. 

Of the retentive Power of the Fertile Soils , 
mentioned by Mr. Bergman. 

This soil contains, as we have already seen, 

Silex - 56 

A r gill - 14 

Calx - 30 

Now the retentive power of 100 parts 

Silex = 25 
Argill = 250 
Calx = 50 
^Consequently the retentive power of 
56 parts Silex = 13 
14 - Argill = 35 
30 - Calx =15 

—•63 



67 

The constitution of the Irish fertile 
soils has not been ascertained, nor has the 
average annual quantity of rain been de- 
termined here. Indeed, the solution of 
the question proposed by the Academy, 
does not strictly require it should, not 
having been limited to any particular coun- 
try : but I should suppose its best soil to 
approach to the nature of that of Upsal, 
the fall of rain being probably between 24 
and 28 inches. In 1792, which was 
reckoned remarkably wet, it was 30 1 in- 
ches in Dublin. 

Before I quit the experiments of Mr. 
Tiliet, it will be proper to mention a few- 
made by him, which seem to invalidate 
the necessity of the presence of the three 
simple earths in fertile soils. 

l mo - In his 26th experiment he tells us, 
he employed only pure sand, such as is 
used for making glass, yet corn grew well 
in it the first year, indifferently the second, 
and nearly failed in the third. Mr. Has- 
senfraz having repeated the experiment 
in pots unperforated, did not find it to 
succeed even the first year, therefore, the 
success^ of Mr. Tiliet was owing to the 
perforation at the bottom of his pot, 
through *which water, impregnated with 
the different earths, and coal must have 



68 

passed. In fact, Mr. Tillet's conclusion 
is contradicted by universal experience. 

2°- In his 28th experiment, in which 
powdered lime-stone only was employed, 
the corn sown prospered exceedingly du- 
ring the three years. To the cause men- 
tioned, in treating of the 26th, I must add, 
that the lime- stone he used was that of St. 
Leu, which contains clay, and consequent- 
ly silex and argill ; it is so porous as to 
admit from 3-19ths to l-5th of its weight 
of water, as Mr. Brisson has shewn ; and 
thus is easily decomposed. The coarse 
powder to which it was reduced answered 
the same purpose as coarse silex ; and the 
iiner might nourish the plants. 

3°- In his 30th experiment he employed 
mere potter's clay ; the grain grew tolera- 
bly well the first year, but perished the se- 
cond ; on the third it flourished most. It 
is hard to draw any specific conclusion 
from this experiment, for it is plain that if 
the texture were not much looser than that 
of clay, the corn could not grow at all, as 
was the case in his 6th and 8th experi- 
ments, already mentioned, and as Mr. 

issenfraz, who repeated this experiment, 
observed. Rain-water might however 

pply a small quantity of calx sufficient 
ibr a small produce of corn . 



69 

I pass over his experiments on old mor- 
tar, as the three earths were evidently con- 
tained in it, though in unknown propor- 
tions. 

Soils on the declivity of hills ouffht to 
be more retentive of water than those ow 
plains as is evident, 



70' 



CHAP. III. 

TO DETERMINE THE COMPOSITION OF A SOIL. 

l mo * IN dry weather, when the soil is 
not over moist nor dry, let a surface of 16 
square inches be cut through to the depth 
of 8 inches ; this may be effected by a right 
angled spade, formed for this particular 
purpose. Of the parallelepiped thus dug 
up, the two inches next the surface should 
be cut off to get rid of the grass, and the 
greater part of the roots ; we shall then 
have a solid 6 inches long, and 16 square 
at the end = 96 cubic inches. Let this be 
weighed ;* its weight will serve to find the 
specific gravity of the soil ; for if 96 cubic 
inches weigh n pounds, 1728 (a cubic 
foot) should weigh x pounds, and x divid- 
ed by 75,954 will express by the quotient 
the specific gravity of the soil. To render 
this and the subsequent operations more 

* Troy weights are generally more exactly made than 
avoirdupois, and therefore should be preferred. A cubic 
foot of pure water weigh?-. 75,945 troy, very nearly, or 62,5 
avoirdupois pounds, at the temperature of 62°. 



71 

intelligible, I should illustrate each by an 
example : Suppose the 96 cubic inches to 
wei^h 6,66 pounds, then 1728 cubic inches 

1§0 
should weigh 1201b. and— = 1,579. 

75,945 
2°- The earth being weighed, is next to 
be broken down and freed from all stony 
substances above the size of a pippin, nnd 
the remainder well mixed together, to ren- 
der the whole as homogeneous as possible; 
then weigh the stones that were picked out, 
andfincUhe proportion belonging to each 
pound of the residuary earth ; call this the 
stony supplement, and demote it by S. Thus 
if the stones weigh 1 lb. = 12 oz. the re- 
mainder, or mere earth, must weigh 5,66ifc. 
and if to 5,661b. there belong 12 oz. of 
stone, to 1 lb. must belong 2, 12014 ozs. or 
2 ozs. 57,66 grains = 1017,66 grs. This 
then is the stony supplement of each suc- 
ceeding pound — S. 

3°- Of the earth thus freed from stony 
matter, take lib — S. (that is the above 
case lib.— 2oz. 57 two thirds grs.) heat 
it nearly to redness in a fiat vessel, often 
stirring it for half an hour, and weigh it 
again when cold. Its loss of weight will 
indicate the quantity of water contained 
in 1 lb. of the soil. Note this loss, and 



t ^ 



call it the watery supplement— W. Suppose 
it in th5s case 100 grains. 

4°- lake another pound of the above 
mass freed from stones, deducing the 
stony and watery supplements ; that is 

1 lb.— S— W, or in the above case lib 

2oz. 57 two-thirds grs. for stone, and— 
100 grains for water; consequently lib. 
— 2 oz. 157 tW- thirds grs. reduce it to 
powder : boil it in four times its weight of 
distilled water for half an hour ; when cool, 
pour it off, first into a coarse linen nitre 
to catch the fibrous particles of roots, and 
then through paper, to catch the finer 
clayey particles diffused through it : set 
by the clear water, add what remains on 
the filtre to the boiled mass : if it be insipid, 
as I suppose it to be, then weigh the fibrous 
matter, and call it the fibrous supplements 
F. Suppose it in the example in hand to 
weigh 10 grs. 

5°- Take two other pounds of the mass 
freed from stony matter, No. II. subtract- 
ing from them the weight of the stony, 
watery, and fibrous substances already 
found; that is, 2 lb— 2 S— 2 W— 2 FV 
pour twice their weight of warm distilled 
water on them, and let them stand twenty- 
four hours or longer; that is, until the water 
has acquired a colour; then pour it off, 



73 

and add more water as long as it changes 
colour ; afterwards filtre the coloured water 
and evaporate it to a pint, or half a pint ; 
set it in a cool place for three days, then 
take out the saline matter, if any be found, 
and set it by. 

6°* Examine the liquor out of which the 
salts have been taken ; if it does not effer- 
vesce with the marine acid, evaporate it 
to dryness, and weigh the residuum ; if it 
does effervesce with acids, saturate it with 
the vitriolic or marine, and evaporate it to 
one fourth of the whole; when cool, take 
out the saline residuum, evaporate the re- 
mainder to dryness, and weigh it: this gives 
the coaly matter, which may be tried by 
projecting it on melted nitre, with which 
it will deflagrate. The half of this coaly 
matter call the coaly supplement of 1 lb. 
I shall suppose it to amount to 12 grs. and 
denote it by C. 

7 0, The filtred water, No. IV. is next to 
be gently evaporated to nearly one pint, 
and then suffered to rest for three days in 
a cool place, that it may deposit its saline 
contents, if it contains any ; and these be- 
ing taken out, the remainder must be eva- 
porated nearly to dryness, and its saline 
and other contents examined. How this 

G 



74 

should be done, I shall not mention, the 
methods being too various, tedious, and of 
too little consequence : few salts occur ex- 
cept gypsum, which is easily distinguish- 
ed. The water may be examined as to 
its saline contents when it is evaporated 
to a pint ; if any salts be found, call them 
the saline supplement, and denote them by 
S. I shall suppose them here = 4 grains. 

8 0, We now return to the boiled earthy 
residuum j No. IV. which we shall sup- 
pose fully freed from its saline matter, as, 
if it be not, it may be easily rendered so, 
by adding more hot water : let it then be 
dried as in No. III. is mentioned. Of 
this earthy matter thus dried, weigh off 
one ounce, deducting one-twelfth part 
of each of the supplements S. W* F. C. 
and S' ; that is, in this case 
1017,66 100 10 

=84,405+ =8,333+—= 

12 12 12 

12 4 

8,333 -f — = 1 + — = 0,3333=95 grs. in all 

12 12 

— then 480 — 95 = 385 grains will remain, 
and represent the mere earthy matter in an 
ounce of the soil. 

9°* Let this remainder be gradually 
thrown into a Florence flask, holding one 



75 

and an half as much spirit of nitre as the 
earth weighs, and also diluted with its own 
weight of water (the acids employed should 
be freed from all contamination of the vi- 
triolic acid;) the next day the flask with 
its contents being again weighed, the dif- 
ference between the weights of the ingre- 
dients and the weights now found, will ex- 
press the quantity of air that escaped dur- 
ing the solution. Thus, in the above 
case, the earth weighing 385 grs. the acid 
577,5 grs. and the water 577,5 grs. in all 
1540 grs. the weight after solution should 
also be 1540, if nothing escaped; but if 
the soil contains calcareous matter, a loss 
will always be found after solution. Let 
us suppose it to amount to 60 grains. 

The weight of air that escaped, furnishes 
us with one method of estimating the quan- 
tity of calcareous matter contained in the 
earth essayed ; for mild calx generally con- 
tains 40 per cent, of air ; then if 40 parts 
air indicate 100 of calcareous matter, 60 
parts air will indicate 150.* 

10°- The solution is then to be carefully 
poured off, and the undissolved mass Wash- 
ed and shaken in distilled water ; the whole 



* I take no account of magnesia, as in agriculture I be^ 
Vieve it of little importance. 



76 

thrown on a fiitre, and sweetened as long- 
as the water that passes through has any 
taste. The contents of this water should 
be precipitated by a solution of mild mine- 
ral alkali : this precipitate also being wash- 
ed and dried in a heat below redness, 
should then be weighed. Thus we have 
another method of finding the weight of 
the calcareous matter. 

11°- The undissolved mass is next to be 
dried in the heat already mentioned, and 
the difference between its weight and the 
weight of the whole earthy mass before 
solution should be noted, as it furnishes a 
third method of discovering the weight of 
the calcareous matter of which it is now 
deprived. Supposing this to amount to 
150 grains, the weight of the undissolved 
residuum should in the above case be 383 
— 150=235 grains. 

12 0, Reduce the dried mass into the 
finest powder, throw it into a Florence 
flabk or glass retort, and pour on it three 
times its weight of pure oil of vitriol, di- 
gest in a strong sand heat, and at last raise 
the heat so as to make the acid boil ; after- 
wards let it evaporate nearly to dryness : 
when cold, pour on it gradually six or 
eight times its weight of distilled water, 



77 

and, after some hours, pour off the solu- 
tion on a filtre ; the filtre should previous- 
ly be weighed, and its edges soaked in 
melted tallow;* the substance found on 
the filtre being weighed (subtracting the 
weight of the filtre) gives the quantity of 
silicious matter ; and this weight subtract- 
ed from that of the dried mass, gives that 
of the argill. In this case I will suppose 
the silicious mass to weigh 140 grains, then 
the argillaceous should weigh 95 grains. 

Then the composition of one pound of 
the soil is as follows : 

Stony matter - 1017,66 

Water - - 100 

Fibres of roots - 10 

Soluble coal - 12 

Saline matter - 4 

Silex 140 x 12 * 1680 

Argill 95x12 = 1140 

Mild calx 150x12 = 1800 



5763,66f 

* An ingenious contrivance of Dr. Black, 
t An error of 3,66 grains for decimals omitted to sub- 
tractions. 



78 



And in centesi 

mal proportion ^ Mild calx 



"Stony matter 18 

Fine silicious 29 

47 

Argill 22 

31 

100 



Its retentive power is 82,25 : hence I 
should judge it to be unfertile in this cli- 
mate unless situated on a declivity, with 
an unimpeded fall. It may be called a 
clayey loam, 

^ Mr. Young discovered a remarkable 
circumstance attendant on fertile soils : he 
found that equal weights of different soils, 
being dried and reduced to powder, afford- 
ed quantities of air by distillation some- 
what corresponding to the ratios of their 
values. This air was a mixture of fixed 
and inflammable airs, both proceeding, 
most probably, from the decomposition of 
water by the coaly matter in the soil. The 
distillation should be made from a retort 
glazed on the outside. He found an ounce 
of dry soil, value five shillings, produced 
ten ounce measures ; 



79 

Of value of from 5 to 12s. produced 28ozs. 
12—20 42 

above 20 66 

This appears to be a good method of esti- 
mating the proportion of coaly matter in 
soils that are in full heart ; that is, not ex- 
hausted, and freed from roots, &c. An- 
other mark of the goodness of a soil is the 
length of the roots of wheat growing in it ; 
for these are an inverse proportion to each 
other, as, if the land be poor, the wheat 
will extend its roots to a great distance ii\ 
quest of food; whereas, if it be rich, they 
will not extend above live or six inches ; 
but of these and some other empyrical 
marks, I shall say no more, as they do not 
tell us the defects of the soils. 



80 



CHAP. IV. 

OF THE MANURES MOST ADVANTAGEOUSLY AP- 
PLICABLE TO THE DIFFERENT SOILS, AND OF 
THE CAUSES OF THEIR BENEFICIAL EFFECT 
IN EACH INSTANCE. 

THE solution of the first part of this 
problem can only be derived from general 
practice of the most skilful farmers, cor- 
rected, however, and improved by the more 
precise determinations and restrictions of 
theory. That of the second, I shall en- 
deavour to deduce solely from the theory 
established in the two last chapters. The 
whole is grounded on this simple propo- 
sition — That manures are applied to sup- 
ply either the defective ingredients of a 
soil, or improve its texture^ or correct its 
vices* 

I now proceed to consider each soil in 
particular. 



81 



of clayey soils. 



The best manure for clayey soils is 
marl : in this all the books of agriculture 
are unanimous ;# and of the different sorts 
of marl, that which is most calcareous is 
best; the silicious next best; limestone- 
gravel best of all ; and argillaceous marl 
least advantageous. f 

Clayey soils are defective both in con- 
stitution and texture ; they want the cal- 
careous ingredient and coarse sand. Cal- 
careous marl supplies the calcareous in- 
gredient chiefly : limestone gravel both. 
The other marls supply them in a lesser 
degree. If the clay be analysed, and its 
proportion of sand and argill known, the 
species of marl most advantageously ap- 
plicable may be determined still better. 
For instance, if the argill notably exceeds 
or even amounts to the proportion of 40 
or 50 per cwt. calcareous marl or lime- 
stone-gravel are the best improving ma- 
nures, as they contain most of the calca- 

* 4th Young's Eastern Tour, 404. 1st Body of Agricul- 
ture, 104, 108. 
f Ibid, 108. 

H 



82 

reous ingredient ; but if the silicious in- 
gredient amounts to 75 or 80 per cwt. as 
it sometimes does, argillaceous marl is 
most suitable. 

A mixture of marl and dung is still 
more advantageous,* because the dung 
supplies the carbonaceous ingredient. But 
the marl must be used in the same quan- 
tity as if dung had not been applied, other- 
wise the operation must be more frequent- 
ly repeated. How the quantity of marl or 
other manure can be estimated, I shall 
presently shew. 

If marl cannot be had, a mixture of 
coarse sand and lime perfectly effete or 
extinguished, or chalk, will answer the 
same purpose, as it will supply the defec- 
tive ingredient, and open the texture of 
the clay ; so also sand alone, or chalk, or 
powdered limestone, may answer, though 
less advantageously. Lime alone appears 
to me less proper, as it is apt to cake, and 
does not sufficiently open the soil. 

Where these manures cannot be had, 
coal ashes, chips of wood, burned clay, 
brick-dust, gravel, or even pebbles, are 
useful ;f for all these improve the texture, 

* 4th Young's Eastern Tour, 404. 

+ 5 Bergman, 107; and You^g-'s Irish Tour, 129,136, 

-149. 



83 

and the former supply also the carbonaceous 
ingredient. 

Before I advance farther, to prevent 
superfluous repetition, I shall lay down a 
second general maxim : which is, That 
dung is a proper ingredient in the appro- 
priated manures of all sorts of soils , as it. 
supplies the carbonaceous principle. 



OF CLAYEY LOAM. 

This soil is defective either in the cal- 
careous ingredient, or in the sandy, or in 
both : if in the first, the proper manure is 
chalk :* if in the second, sand ; if in both, 
silicious marl or limestone-gravel, or effete 
lime and sand. 

The quantity of chalk that should be 
employed, considered abstractedly, should 
be directly proportional to the defect of 
calcareous matter ; but as such a quantity 
cannot be added without diminishing the 
proportion of one of the other ingredients, 
a much smaller quantity must be employ- 
ed, or else a substance which may convey 

* 1st Young's Eastern Tour, 395.< 



84 

some proportion of the other ingredient. 
The same observation holds also with re- 
spect to sand. Thus we have seen, in 
the last chapter, a clayey loam, in which 
the sandy ingredient was defective, and the 
argillaceous superabundant, but the calca- 
reous exact. Its composition stood thus : 

Sand and Gravel - - 47 

Argill 22 

Mild Calx - - \ - 31 

Here the sandy part wants 10 per cwt. 
the argill is superabundant ; but we can- 
not increase the proportion of sand with- 
out diminishing that of calx. Hence 
we must either use a smaller propor- 
tion of sandy ingredient than its defect 
requires, or apply a substance that 
would supply some proportion of the cal- 
careous ingredient also : such are lime- 
stone-gravel, silicious marl, effete lime, 
mixed with sand, or pounded limestone. 
Suppose the proportion of the substance 
to be employed were six per cwt. ; that is, 
six pound for every hundred pounds of 
the soil, then the quantity requisite for an 
acre may be calculated thus : a square 
foot of this soil, cut down to the depth of 
fourteen inches, and paring off the two up- 



85 

permost, as consisting chiefly of roots, &c, 
weighs, as we have seen, 120 lb. ; and if 
100 lb. requires six of the manure, 1201b. 
will require 7,2 ; therefore every square 
foot of the soil will require 7,2 of the ma- 
nure : now an English acre contains 43560 
square feet ; and consequently 43560 mul- 
tiplied into 7,2 of the manure = 3136321b. 
or 208 cart loads, reckoning 15001b. to 
the cart load. 



CHALKY SOILS. 



This soil wants both the argillaceous 
and the stony, sandy, or gravelly ingredi- 
ents ; therefore the best manure for it is 
clayey loam, or sandy loam;* but when 
the chalk is so hard, as it frequently is in 
England, and so difficultly reducible to 
impalpable powder as to keep of itself the 
soil sufficiently open, then clay is the best 
manure,! as in such cases the coarse sand 
or gravelly ingredients of loams are of no 
use. Some think, it is true, that pebbles 
in a field serve to preserve or communi- 



* 5 Berg-man, 107. 

f Young's Eastern Tour. 



86 

cate heat. This use, however, is not suf- 
ficiently ascertained. 



CHALKY LOAM. 

The best manure for this soil is clay, 
or argillaceous marl,* if clay cannot be 
had ; because this soil is defective princi- 
pally in the argillaceous ingredient. In 
Ireland, chalkv soils or loams seldom oc- 
cur, but light limestone soils frequently, 
and these do not differ essentially from 
chalky loams poor in argill: clay, there- 
fore, and often the soil of bogs, should serve 
as a manure for them. 



SANDY SOILS. 

The best manure for these is calcerous 
marl,f which exactly corresponds with our 
theory ; for these soils want both the argil- 
laceous and calcerous ingredients ; and 
this marl supplies both : the next best is 
argillaceous marl ; and next to these, clay, 
mixed with lime, or calcareous, or clayey 



* 4th Young's Eastern Tour, 404 
f Ibid. 401, 412. 



87 

loams. In Norfolk, they seem to value 
clay more than marl, probably because 
their sandy soils already contain calcareous 
parts; possibly, also, they misname marl, 
calling mere chalk by that name. Lime 
or chalk are less proper, as they do not give 
sufficient coherence to the soil ; however, 
when mixed with earth or dung, they an- 
swer well,* because they form a sort of 
marl or compound, comprehending the de- 
fective ingredients. 



SANDY LOAMS. 

These are defective chiefly in the calca- 
reous ingredient, and, in some degree, also 
in the argillaceous; their texture too is im- 
perfect, as they abound both in line and 
coarse sand; chalk or lime would supply 
the first defect, but would leave the texture 
unamended. Hence they are used when 
better cannot be had;f yet calcareous or 
argillaceous marls are most proper. ± 
Clay, after land has been chalked, answers, 



* Young's Eastern Tour, 597. 

t 4th Young's Eastern Tour, 398. 

i Ibid. 402. 



88 

as we are told, remarkably well, because 
it remedies the texture.* 



GRAVELLY LOAMS. 

These soils are benefited by the appli- 
cation of marl, whether argillaceous or 
calcareous,! for reasons which I suppose 
are now apparent : if the gravel be calca- 
reous, clay may be employed. J A mix- 
ture of effete lime and clay should answer 
in all cases. 



TILL AND VITRIOLIC SOILS. 

These necessarily require the calcareous 
ingredient to neutralize their peccant acid : 
hence chalk, limestone-gravel, lime and 
calcareous marl, are most advantageously 
applied to them. 

Home, 35. 



BOGS, OR BOGGY SOILS. 

When these are well dried by sufficient 

* 4lh Young's Annals, 413. 

f 4th Young's Eastern Tojir, 404, 406 

I 1st Eaiftern Tour. 



89 

drains, the nature of their soil should be 
explored by analysis, and an appropriate 
manure applied. In general, they should 
first be burned, if capable of that operation, 
then gravelled. If their upper parts con- 
tain a sufficiency of the carbonaceous prin- 
ciple, as often happens, they need not be 
burned. Limestone-gravel will answer 
best, or lime mixed with coarse sand or 
gravel, because in general they are of a 
clayey nature ; if more sandy, lime may 
answer well, or calcareous marl. The 
preference in these cases must be decided 
by analysis.* 



HEATHY SOILS. 

These should first be burned, to destroy 
the heath and increase the carbonaceous 
principle : they should then be analysed, 
and the defective principles supplied. 
Lime is said to destroy heath, and so is 
limestone-gravel :f this is fittest when the 
soil is clayey; lime when it is graveily.i 
Gypsum also answers remarkably well 
when the soils are dry. 

* Young's Iris!) Tour, 233, 223. 
f 4i h Y.ntncrVEtistern T i;r, 396. 
' I-Mi Ten/ ;i°. 



90 



OF SOME PARTICULAR MANURES. 

We have now stated most of the known 
soils, and mention the manures which 
tend most to their improvement : there 
are, however some others whose mode of 
action is not generally understood, and 
whose nature it will therefore be proper 
to explain. 



OE PARING AND BURNING. 

This mode of improvement is not par~ 
ticular to any species of soil, though poor 
soils that have few vegetables growing in 
them, will certainly profit least by it. 

Its advantages are, 

First, that it converts vegetables and 
their roots into coal. Hence it is that ag- 
ricultural writers tell us, though without 
# knowing the reason, that all violence of 
fire is to be avoided, and that a slow 
smothering fire is best.* 

Secondly, That it destroys the old sickly 
roots, and thus leaves room for other? 
younger and more vigorous. 

♦ 1st Body Of Agriculture, 210, 21 h 



91 

Many have imagined that it diminishes 
and consumes the soil ; but repeated ex- 
perience has shewn the contrary. I need 
only mention that of Colonel St. Leger, 
in Yorkshire, related by Mr. Young in 
the 1st volume of his Eastern Tour, p. 
182. It is well known that clays and 
loams are rather hardened than consumed 
by heat. However, unless fresh seeds be 
committed, the soil will be unproductive 
for a number of years ; the coaly principle 
may also be exhausted by too many crops. 



OF GYPSUM- 

This manure was discovered by Mr. 
Mayer, a German clergyman of uncom- 
mon merit, in the year 1768 : it has since 
been applied with signal success in Ger- 
many, Switzerland, France, and America. 

If in England it has not been so much 
approved of, it must be because the calca- 
reous principle prevails there almost uni- 
versally : clayey lands are most improved 
by it.. The time for spreading it is Fe- 
bruary or March, and then it is to be 
thinly strewed on the land at the rate of 
about eight bushels to the acre : more 
would be hurtful. The rationale of its 



92 

effects may be deduced from its extraordi- 
nary septic power, for it is found to acce- 
lerate putrefaction in a higher degree than 
any other substance ;* and hence it is not 
ploughed in like other manures, but bare- 
ly strewed on the surface of the land ; and 
in the month of February, to convert the 
old grass quickly into coal, to nourish the 
young growth. 

2dly. From its being itself no inconsi- 
derable part of the food of many plants, 
particularly of clover, pulse, and corn, but 
the land on which it is strewed must be 
dry, such as would naturally suit clover, 
Sec. otherwise it would be useless. 

Thus far I have endeavoured to illus- 
trate the important subject proposed by 
the Academy, collecting and reflecting 
upon it the scattered rays resulting from 
the latest chemical researches. The inti- 
mate connexion between many of these, 
seemingly the most abstract and remote, 
with the hidden process of nature, may 
now be clearly perceived. These grand 
and complicated operations, like a well 
fortified town, cannot be mastered by storm 
or a coup- de-main ; the approaches must 
be made at a distance, and almost unseenv 

» Histoire de la Putrefaction, 3t>- 



93 

Hence we may infer how little can be ex- 
pected from agricultural societies that do 
not unite chemistry and meteorology with 
their principal object. 

With respect to the question at present 
before us, the great desiderata seem to be, 
How to render charcoal soluble in water 
for the purpose of vegetation : and, to dis- 
cover that composition of the different 
earths best suited to detain or exhale the 
due proportion of the average quantity 
of moisture that falls in each particular 
country. On this relation, or adaptation, 
we have seen that the fertility of each es- 
sentially depends : we must also have per- 
ceived, that to a regular and systematic 
improvement of soils, a knowledge of their 
defects, and of the quantum of their de- 
fects, is absolutely necessary.. This in- 
formation can be conveyed only by a che- 
mical analysis. Country farmers (at least 
as long as the present absurd mode of edu- 
cation prevails) cannot be expected to pos- 
sess sufficient skill to execute the necessary 
procesess: but country apothecaries cer- 
tainly may. The profit arising from sucli 
experiments (should the public encourage 
them) would sufficiently excite them to 
acquire a branch of knowledge so nearly, 
allied with their profession. In the mean 



94 

time, soils might be sent to some skilful 
persons in the capital by country gentle- 
men ; who would thus be enabled to as- 
certain and appreciate the advantages at- 
tending such researches, and enlighten and 
encourage their more ignorant and diffi- 
dent neighbours. Many of them might, 
perhaps, themselves feel a taste for occupa- 
tions of this nature : occupation swhich not 
only fully suffice to fill up the many vacant 
hours and days which the solitude of a 
country life must frequently leave them, 
but are, moreover, sweetened by the plea- 
sing recollection, that, of all others, they 
tend most directly to the general happi- 
ness of mankind. 

AGRICOLA 



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